In tubers, such as onion plants, the edible bulb part of the plant is below ground, while a leafy top extends above ground. An acre of commercial onions can contain between 80,000 and 150,000 plants, with each bulb weighing between 1/2 to 2 lbs., and with the green leafy top or stalk portion weighing almost as much as the bulb. Upon reaching maturity, the stalks of the onions wither and fall onto the ground. The bent stalks lie all over the ground and hinder visibility of, and ready access to, the ripe bulbs. The harvesting process is complicated by the matted covering of the onion tops on the ground. Some onion plants, referred to as seeders, keep growing and have green upright stalks, in contrast to the mature onions which have stalks that are bent, withered and dried. The seeders, which may make up 5-10%, or more, of the total crop yield, create a non-homogeneous crop surface which further hinders harvesting operations.
Currently, onions are uprooted by a breaker bar which is pulled below the onions to thrust the onions out of the ground. After drying for a few days, the onions are manually topped by grabbing the onion stalks and using scissors to cut off the tops, after which the onions are mechanically or manually gathered, and taken to a facility for packing or storage.
In some cases, the uprooted, untopped onions are mechanically gathered and taken to a packing area where the onions are again manually topped with scissors or clippers. All onion residues are discarded at this stage if they have not been eliminated earlier. Because the onion tops are acidic, the disposal of large quantities of onion tops gathered at the packing facilities becomes a great environmental concern, with attendant difficulties in environmentally safe disposal of large quantities of tops.
As the onion crop becomes ripe and ready for harvesting at about the same time in a given geographical region, large numbers of workers must be employed to accomplish the manual topping task. This manual labor is very expensive, and creates significant uncertainties in arranging and coordinating sufficient numbers of workers, if they are even available when needed.
While several patents disclose equipment to top onions and tubers, no such equipment is commercially used today in the United States. For example, patents to Davis (U.S. Pat. No. 1,347,733) and Sampson (U.S. Pat. No. 2,579,013) both disclose a machine for raising and cutting potato-vines and the like, and onions, respectively. In both cases, a rotary fan mounted on a wheeled frame raises the vines and onion tops for cutting. Sampson also uses a rotating belt with canvas cross-flights to push the onions up an inclined trough which ends near the rear of the frame where a crate can be positioned to receive the topped onions. A disadvantage of both devices is that only a small area below the fans can be harvested. Another disadvantage is the distribution of whole, severed vines back onto the field, covering the crops on adjacent rows which then are difficult to locate and harvest.
The Kinch patent, U.S. Pat. No. 4,757,670, describes an agricultural crop defoliator which uses a blowing technique to elevate the tops of plants for cutting. A rotating cutting blade is used that is also height-adjustable. However, rotating blades are not believed suitable for cutting some vegetable tops, such as onion tops, cleanly, as they tear the tops. This damages the bulbs, or causes the torn portion to rot. In addition, the severed tops are again left intact to be distributed over, and obstruct, access to the onions on the adjacent ground which then need to be gathered up.
Soviet Union Patent No. 3840-660-A, issued to Vege, discloses a stem cutter for trimming onion haulms (stalks). Rotating elastic rods lift the tops of the plants to come in contact with rotating blades inside a drum.
The designs of the prior devices which use suction to lift the plants are such that they harvest but one row of crops at a time. That increases the time needed to harvest a field of crops. There is thus a need for a device which can top large areas of crops at the same time.
As these machines pass over the onion field, their vacuum intakes, blower casings and elastic rods bend the plant tops. The tops are believed to meet each cutting implement at an inclined angle. The cutting implements disclosed above are oriented horizontally, and while some can move vertically, they are not designed to change this horizontal orientation. There is thus a need for a cutting blade which can cut the tops at a more perpendicular angle to the vegetable or onion top.
The harvesting equipment described in the above-mentioned patents share the common disadvantage of being cumbersome to maneuver around sharp corners, requiring large areas at the ends of the fields to allow the devices to be turned. Sampson, Kinch and Vege show simple towed devices which restrict the arc of turn to that which avoids jack-knifing or collision between the towing and towed vehicles. Davis allows for steering wheels on the front which would limit the arc of turn to that allowed by the wheel base of the device. There is thus a need for a device with steering that enables sharp corners to be made, so that more crops can be planted in the fields.
Whatever the claimed advantages of the prior equipment, the current widespread use of inefficient and costly manual labor demonstrates that these prior inventions did not succeed. There exists a need for a mechanical topper that addresses the above needs, and overcomes the drawbacks of prior vegetable topping machines by increasing the harvesting efficiency without damaging the tubers.